Merge 3.4 (datetime rounding)

2 files changed, 39 insertions, 34 deletions

diff --git a/Lib/datetime.py b/Lib/datetime.py
index db13b12..b9719cb 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -1366,28 +1366,34 @@ class datetime(date):
         return self._tzinfo
 
     @classmethod
-    def fromtimestamp(cls, t, tz=None):
+    def _fromtimestamp(cls, t, utc, tz):
         """Construct a datetime from a POSIX timestamp (like time.time()).
 
         A timezone info object may be passed in as well.
         """
-        _check_tzinfo_arg(tz)
-
-        converter = _time.localtime if tz is None else _time.gmtime
-
-        t, frac = divmod(t, 1.0)
-        us = int(frac * 1e6)
-
-        # If timestamp is less than one microsecond smaller than a
-        # full second, us can be rounded up to 1000000.  In this case,
-        # roll over to seconds, otherwise, ValueError is raised
-        # by the constructor.
-        if us == 1000000:
+        frac, t = _math.modf(t)
+        us = round(frac * 1e6)
+        if us >= 1000000:
             t += 1
-            us = 0
+            us -= 1000000
+        elif us < 0:
+            t -= 1
+            us += 1000000
+
+        converter = _time.gmtime if utc else _time.localtime
         y, m, d, hh, mm, ss, weekday, jday, dst = converter(t)
         ss = min(ss, 59)    # clamp out leap seconds if the platform has them
-        result = cls(y, m, d, hh, mm, ss, us, tz)
+        return cls(y, m, d, hh, mm, ss, us, tz)
+
+    @classmethod
+    def fromtimestamp(cls, t, tz=None):
+        """Construct a datetime from a POSIX timestamp (like time.time()).
+
+        A timezone info object may be passed in as well.
+        """
+        _check_tzinfo_arg(tz)
+
+        result = cls._fromtimestamp(t, tz is not None, tz)
         if tz is not None:
             result = tz.fromutc(result)
         return result
@@ -1395,19 +1401,7 @@ class datetime(date):
     @classmethod
     def utcfromtimestamp(cls, t):
         """Construct a naive UTC datetime from a POSIX timestamp."""
-        t, frac = divmod(t, 1.0)
-        us = int(frac * 1e6)
-
-        # If timestamp is less than one microsecond smaller than a
-        # full second, us can be rounded up to 1000000.  In this case,
-        # roll over to seconds, otherwise, ValueError is raised
-        # by the constructor.
-        if us == 1000000:
-            t += 1
-            us = 0
-        y, m, d, hh, mm, ss, weekday, jday, dst = _time.gmtime(t)
-        ss = min(ss, 59)    # clamp out leap seconds if the platform has them
-        return cls(y, m, d, hh, mm, ss, us)
+        return cls._fromtimestamp(t, True, None)
 
     @classmethod
     def now(cls, tz=None):
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index babeb44..357fe13 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -663,11 +663,15 @@ class TestTimeDelta(HarmlessMixedComparison, unittest.TestCase):
         eq(td(milliseconds=0.4/1000), td(0))    # rounds to 0
         eq(td(milliseconds=-0.4/1000), td(0))    # rounds to 0
         eq(td(milliseconds=0.5/1000), td(microseconds=0))
-        eq(td(milliseconds=-0.5/1000), td(microseconds=0))
+        eq(td(milliseconds=-0.5/1000), td(microseconds=-0))
         eq(td(milliseconds=0.6/1000), td(microseconds=1))
         eq(td(milliseconds=-0.6/1000), td(microseconds=-1))
+        eq(td(milliseconds=1.5/1000), td(microseconds=2))
+        eq(td(milliseconds=-1.5/1000), td(microseconds=-2))
         eq(td(seconds=0.5/10**6), td(microseconds=0))
-        eq(td(seconds=-0.5/10**6), td(microseconds=0))
+        eq(td(seconds=-0.5/10**6), td(microseconds=-0))
+        eq(td(seconds=1/2**7), td(microseconds=7812))
+        eq(td(seconds=-1/2**7), td(microseconds=-7812))
 
         # Rounding due to contributions from more than one field.
         us_per_hour = 3600e6
@@ -1851,6 +1855,7 @@ class TestDateTime(TestDate):
             zero = fts(0)
             self.assertEqual(zero.second, 0)
             self.assertEqual(zero.microsecond, 0)
+            one = fts(1e-6)
             try:
                 minus_one = fts(-1e-6)
             except OSError:
@@ -1861,22 +1866,28 @@ class TestDateTime(TestDate):
                 self.assertEqual(minus_one.microsecond, 999999)
 
                 t = fts(-1e-8)
-                self.assertEqual(t, minus_one)
+                self.assertEqual(t, zero)
                 t = fts(-9e-7)
                 self.assertEqual(t, minus_one)
                 t = fts(-1e-7)
-                self.assertEqual(t, minus_one)
+                self.assertEqual(t, zero)
+                t = fts(-1/2**7)
+                self.assertEqual(t.second, 59)
+                self.assertEqual(t.microsecond, 992188)
 
             t = fts(1e-7)
             self.assertEqual(t, zero)
             t = fts(9e-7)
-            self.assertEqual(t, zero)
+            self.assertEqual(t, one)
             t = fts(0.99999949)
             self.assertEqual(t.second, 0)
             self.assertEqual(t.microsecond, 999999)
             t = fts(0.9999999)
+            self.assertEqual(t.second, 1)
+            self.assertEqual(t.microsecond, 0)
+            t = fts(1/2**7)
             self.assertEqual(t.second, 0)
-            self.assertEqual(t.microsecond, 999999)
+            self.assertEqual(t.microsecond, 7812)
 
     def test_insane_fromtimestamp(self):
         # It's possible that some platform maps time_t to double,